Second Range Without TCC Applied

Before shifting from first to second range, the transmission control module (TCM) makes certain shift valve 1, shift valve 2, and shift valve 3 are in the correct position with shift valve 1 and shift valve 2 de-stroked and shift valve 3 stroked.

Pressure control solenoid 1 (PCS1) is energized, opening PCS1 signal pressure to exhaust and allowing pressure control valve 1 to de-stroke, exhausting the low and reverse clutch pressure. PCS2 is energized, raising PCS2 signal and PCS2 pressures. The PCS2 pressure is directed through shift valve 1 and shift valve 3 to the 2-6 clutch. The TCM provides current to PCS2, which controls the rate at which the pressure control valve 2 supplies pressure to the 2-6 clutch, and current to PCS1, which controls the rate at which the low and reverse clutch is exhausted, assuring a smooth transition to second range. Main pressure continues to feed through shift valve 3 and the manual selector valve, keeping the 1-2-3-4 clutch applied.

The combination of the 1-2-3-4 and the 2-6 clutch application produces second range operation.

After the shift to second range is complete, SS2 is de-energized allowing shift valve 2 to de-stroke. The low and reverse clutch feed, which was exhausted through shift valve 2 and the PCS1, now exhausts through exhaust backfill, keeping the low and reverse clutch released. The 3rd, 5th, and reverse clutch has an exhaust path through shift valve 2 to the pressure control valve 1, keeping the 3rd, 5th, and reverse clutch released.

Pressure switch 1, pressure switch 2, and pressure switch 3 turn off, providing feedback that the valves are in the de-stroked position.

If electrical power is interrupted while the transmission is in second range, PCS1 and PCS2 de-energize. Normally open PCS2 exhausts the PCS2 signal pressure, allowing pressure control valve 2 to de-stroke, exhausting the 2-6 clutch. Normally closed PCS1 blocks the exhaust of the pressure control valve 1 signal pressure, allowing the PCS1 signal and PCS1 pressures to rise. Pressure control valve 1 directs full pressure through shift valve 2 to the 3rd, 5th, and reverse clutch, applying the clutch. The 1-2-3-4 clutch continues to be applied with main pressure through shift valve 3 and the manual selector valve. The combination of the 1-2-3-4 clutch and the 3rd, 5th, and reverse clutch applied produces third range converter operation for limp home capability.

If the torque converter clutch was applied during the power interrupt, the TCC solenoid is de-energized and the transmission returns to converter operation.

If electrical power is interrupted while the transmission is in second range and subsequent third range operation, moving the manual selector valve to Neutral (N) will cut off main pressure to the 1-2-3-4 clutch and the clutch will be exhausted. The 3rd, 5th, and reverse clutch remains applied. Because only one clutch is applied, the transmission goes to neutral.

If electrical power is interrupted while the transmission is in second range with subsequent third range operation, moving the manual selector valve to reverse will cut off main pressure to the 1-2-3-4 clutch, exhausting the 1-2-3-4 clutch. The manual selector directs main pressure through the TCC valve and shift valve 2 to the low and reverse clutch, applying the clutch. The 3rd, 5th and reverse clutch remains applied. The combination of the 3rd, 5th, and reverse clutch and the low and reverse clutch application produces reverse range operation for limp home capability.

Second Range With TCC Applied (Tow-Haul)

Energizing the torque converter clutch (TCC) solenoid strokes the TCC valve against the stop, allowing main pressure to flow to the top of the converter flow valve. The converter flow valve is stroked, exhausting converter-in pressure to sump, and eliminating the separating force between the TCC piston and the converter cover. At the same time, the converter flow valve opens the passage supplying TCC-apply pressure to the converter-out circuit. The pressure differential across the TCC piston applies the torque converter clutch.

Depending upon the calibration, TCC solenoid could be energized in ranges 2-6. The calibrations can also apply the TCC for special applications such as power take-off (PTO) operation controlled directly by engine speed with transmission in neutral or TCC operation in first hold.